Field of the Invention
The present invention relates to a display apparatus capable of rotating and displaying an image in accordance with a detected apparatus attitude, and a control method thereof.
Description of the Related Art
In recent years, not only a digital camera and a video camera but also a portable telephone, a music player, and the like are provided with a camera unit or a display unit such as an LCD (liquid crystal display) monitor to allow a user to capture or view a still image or a moving image. In addition, loading the moving image data of TV programs and the like recorded at home into the above-described equipments and tools and viewing them away from home have been widespread.
An image pickup apparatus such as a digital camera is designed supposing to basically handle a horizontal image having an aspect ratio of 4:3 or 16:9 in consideration of the display environment of a conventional TV monitor or the like. For this reason, a monitor unit formed from an LCD or the like also normally has a rectangular screen having an aspect ratio of 4:3 or 16:9.
FIG. 9 is a view showing an example of the photographing attitude of a digital camera 900. When the user holds the digital camera 900 in a normal attitude, as shown in FIG. 9, a horizontal image can be photographed. Hence, the monitor screen is designed to be long in the horizontal direction in accordance with the photographed image. The photographing attitude shown in FIG. 9 will be referred to as a horizontally-oriented attitude, and a photographed image obtained by performing photographing in the horizontally-oriented attitude will be referred to as a horizontally-oriented image hereinafter.
On the other hand, the user also often performs photographing while holding the digital camera 900 rotated by 90° with respect to the horizontally-oriented attitude, as shown in FIG. 10. The attitude shown in FIG. 10 aims at obtaining a vertical image. This photographing attitude will be referred to as a vertically-oriented attitude, and a photographed image obtained by performing photographing in the vertically-oriented attitude will be referred to as a vertically-oriented image hereinafter.
As described above, it is possible to obtain a horizontally-long horizontally-oriented image and a vertically-long vertically-oriented image by changing the manner to hold the digital camera. There is also known a technique of detecting the attitude of the digital camera using a tilt sensor or the like, adding flag information to image data as information (attitude-at-photographing information) representing the digital camera holding manner in photographing, and using the added information for image playback or editing later.
FIGS. 11 to 14 are views showing examples of image display states on the digital camera 900.
FIG. 11 is a view showing a state in which a horizontally-oriented image is displayed in the horizontally-oriented attitude. When the digital camera 900 is set in the horizontally-oriented attitude, the horizontally-oriented image photographed in the horizontally-oriented attitude is displayed so as to fill the monitor screen.
FIG. 12 is a view showing a state in which a vertically-oriented image is displayed in the horizontally-oriented attitude. In this case, the image is rotated and reduced by referring to the above-described flag information, and converted into an image whose long-side length coincides with the short-side length of the monitor screen. The image is displayed while making its top and bottom direction at the time of photographing coincide with the top and bottom direction of the digital camera 900. The short-side length of the image does not coincide with the long-side length of the monitor screen. Hence, so-called letterbox display is performed by performing a process of adding black bands 1201 to the left and right sides of the image to make the horizontal and vertical sizes of the image coincide with those of the monitor screen.
FIG. 13 is a view showing a state in which the vertically-oriented image is displayed in the vertically-oriented attitude. In the example shown in FIG. 13, since the horizontal and vertical sizes of the image coincide with those of the monitor screen, the image is displayed so as to fill the monitor screen. FIG. 14 is a view showing a state in which the horizontally-oriented image is displayed in the vertically-oriented attitude. In the example shown in FIG. 14, the horizontally-oriented image which is rotated and reduced is letterbox-displayed, as in the example shown in FIG. 12.
As described above, the top and bottom, or upwards and downwards, direction of the display image can be changed in accordance with the equipment or tool attitude at the time of playback using the attitude-at-photographing information added to the image. Note that the above-described photographing attitude switching and the image playback method using attitude-at-photographing information are applicable not only to a still image but also to a moving image, or not only to a digital camera but also to a video camera, a portable telephone, and the like. The following related arts are disclosed as techniques of rotating a display image correspondingly to the equipment or tool attitude.
Japanese Patent Application Laid-Open No. 2006-166248 discloses a technique capable of switching between a first display attitude in which the longitudinal direction of an image becomes perpendicular to the longitudinal direction of the display screen and a second display attitude in which the longitudinal direction of an image almost coincides with the longitudinal direction of the display screen, when displaying a horizontal image on a horizontally-long display screen. According to this technique, switching between the first and second display attitudes is done in accordance with the operation mode or attitude of the equipment or tool.
Japanese Patent Application Laid-Open No. 2008-066967 discloses a technique of performing a rotation process of an image based on the attitude information of an apparatus during the stop of moving image data playback, and displaying the image. In this technique, after the start of playback or after the elapse of a predetermined time from the start of playback, the image is displayed in the immediately preceding image display direction independently of the attitude of the apparatus, and then the rotation process is not performed.
When magnifying an image so that the entire image fits in the display area, a horizontally-oriented image can be displayed larger by making its top and bottom direction coincide with the short-length direction of the display as shown in FIG. 11, than by making the top and bottom direction coincide with the longitudinal direction as shown in FIG. 14. On the other hand, a vertically-oriented image can be displayed larger by making its top and bottom direction coincide with the longitudinal direction of the display as shown in FIG. 13, than by making the top and bottom direction coincide with the short-length direction as shown in FIG. 12. In order to expand the view of an image, the user preferably rotates the playback apparatus to the attitude in FIG. 11 or 13. However, if the display time of a moving image is only several sec, playback may end during changing the apparatus attitude in accordance with the image, and the user may be unable to sufficiently view the image.
In general, an image is preferably viewed while being displayed on the entire monitor screen regardless of whether it is a moving image or a still image. This tendency becomes more conspicuous in portable equipments and tools in which the monitor screen size is limited as the equipment or tool is downsized. It is therefore recommended to view each of a horizontally-oriented image and a vertically-oriented image in an optimum attitude, as shown in FIGS. 11 and 13.
When viewing a still image, the contents do not change. However, a moving image has a time base, and its contents change in accordance with the movement of the object along with the elapse of time. In addition, the time of length of a moving image variously changes for each file. Some moving images may end in several sec, and some may take several tens of minutes to play back. For example, when sequentially switching and displaying a plurality of images for slide show display or the like, the time to display one image can arbitrarily be determined for a still image. However, a moving image needs to be played back along the actual time base except in special playback such as slow motion or fast-forward.
As described above, a moving image is restricted by the time base in playback. For this reason, when continuously playing back a moving image group including both horizontal moving images and vertical moving images, the apparatus attitude needs to be frequently changed if the times of the respective moving images are short. Especially, a moving image whose display time is several sec ends during changing the apparatus attitude in accordance with the image, and the playback of the next moving image starts without allowing the user to sufficiently view the image. When horizontal and vertical moving images having short display times are irregularly arranged, the operation of confirming the display image and rotating the apparatus to make its attitude coincide with the image cannot be performed sufficiently without delay because the moving image switches at a high speed.
In addition, the apparatus attitude may change during moving image playback. For example, when the user changes the hand to hold a portable equipment or tool, or stands up or sits down, the apparatus attitude may change against his/her intention. If the apparatus attitude is monitored using a sensor, and the display image is changed by rotation or enlargement/reduction, as described above, the image responds to the change in the apparatus attitude against user's intention. This may cause an unintentional change in the orientation or size of the display image, and the user readily misses the object image of interest. If the display time of the moving image is short, playback of the next moving image may start before the user finds the object image.